Line cookie sheet with foil. Spray with cooking spray. Lay saltines on cookie sheet single layer with sides touching. In sauce pan, melt butter. Add brown sugar and boil for 3 minutes. Spread over crackers. Bake 5 minutes at 350 degrees. While hot, evenly sprinkle with chocolate chips. Cover with foils and seal edges. Wait 3 minutes. Uncover. Spread chocolate with knife. Cover. Freeze 20 minutes. Break apart crackers.